Copolymer compositions particularly useful as additives for hydrocarbon oils

ABSTRACT

New compositions, useful as viscosity additives, having dispersing properties in various hydrocarbon oils, are disclosed, which comprise: 
     recurrent units derived from one or more acrylic or methacrylic esters (e.g. 55-99.8% by weight), 
     recurrent units derived from one or more nitrogenous vinyl monomers obtained by reacting triallylcyanurate with aliphatic amines or polyamines (e.g. 0.2-10% by weight), and optionally 
     recurrent units derived from one or more vinyl aromatic monomers (e.g. 0-35% by weight). 
     These copolymer compositions generally have a weight average molecular weight from 30,000 to 800,000 and a polydispersity generally lower than 5. They can be prepared by any radical copolymerization process using for example azoic or peroxydic initiators. 
     The copolymer compositions considered are used as additives for improving the rheological properties of hydrocarbon oils. In addition, they exhibit good dispersing properties.

This is a division of application Ser. No. 07/060,785 filed June 12, 1987 now U.S. Pat. No. 4,882,404.

BACKGROUND OF THE INVENTION

It is known to incorporate with conventional flow additives for hydrocarbon oils compounds which impart to them dispersing properties.

The different categories of so-called viscosity additives, particularly used in motor oil compositions (for improving the thickening power, the selectivity, the freezing point, the shearing strength, etc ... ) are disclosed in detail, for example, by J. Briant and coll. in the work "Proprietes rheologiques des lubrifiants" Editions TECHNIP, Paris.

The incorporation by copolymerisation, grafting, esterification or maleinization, of radicals carrying groups generally of the nitrogenous or oxygenated type, give dispersing properties to these additives. Accordingly, the dispersing additive amount required in the lubricating oil composition may be substantially reduced. The most currently used monomers for copolymerization or grafting are 4-vinyl pyridine, N-vinyl pyrrolidone and N-vinyl imidazole. The different compounds used to impart dispersing properties to viscosity additives are more exhaustively listed in the above-mentioned work.

The product obtained by reaction of one or more polyisobutene-succinimides with triazine trichloride (U.S. Pat. No. 4,116,875) is also known as dispersing additive.

Finally, it is known to prepare compounds of high nitrogen content, which may be used for stabilizing polyolefins by protecting them against hot oxidation ("Synthesis" pages 182-185, March 1975), by aminolysis of triallylcyanurate with primary amines.

SUMMARY OF THE INVENTION

Now, new copolymer compounds have been discovered which offer very advantageous properties as additives in various hydrocarbon oils, as well by their action on the rheological properties of the oil and by their dispersing effect.

The copolymer compositions of the invention may be generally defined by the fact that they comprise recurrent units derived from one or more acrylic esters, from one or more monomers obtained by reaction of aliphatic amines or polyamines with triallylcyanurate, and optionally from one or more vinylaromatic monomers.

More particularly, the copolymer compositions of the invention, which may be prepared by radical copolymerization, contain 0-35% by weight of one or more vinylaromatic monomers, 55-99.8% by weight of one or more monomers of linear or branched alkyl acrylate or methacrylate type, comprising 1-22 carbon atoms, and from 0.2 to 10% by weight of one or more nitrogenous vinyl monomers derived from triallylcyanurate. The proportion of nitrogenous vinyl monomer is advantageously from 0.5 to 4% by weight, the proportions of the other monomers being correspondingly adjusted.

Nitrogenous vinyl monomers, the use of which in the preparation of the polymers according to the invention is the main characteristic thereof, are prepared more particularly by reacting triallylcyanurate with one or more amines or polyamines complying with the general formula: ##STR1## wherein R¹ is a hydrogen atom or a linear or branched alkyl radical of 1-24 carbon atoms (--C_(n) H_(2n+1)), x ranges from 1 to 10 or may be 0 when n is at least 4, R², defined when x is not zero, represents the hydrogen atom or a linear or branched alkyl radical of 1-24 carbon atoms (--C_(m) H_(2m+1)), and A, also defined when x is not zero, represents an alkylene radical, for example of 2-6 carbon atoms, more particularly the ethylene, propylene or isopropylene radical.

Examples of amines to be used are:

monoprimary monoamines of formula R¹ NH₂, such for example as n-butylamine, sec-butylamine, tert-butylamine, n-pentylamine, 4, 3 or 2 methyl-n-butylamine, n-hexylamine, n-heptylamine, n-octylamine, n-nonylamine, eicosylamine and docosylamine; as well as their isomers;

monoprimary polyamines of formula ##STR2## such for example as N, N-dimethyl ethylenediamine, N-oleyl propane diamine, N, N-dimethyl diamino-propane, N, N-diethyl diamino-propane, N, N dimethyl diamino-isopropane, etc; and

biprimary polyamines of formula H-(NH-A)_(x) NH₂, such for example as ethylene diamine, propylene diamine, diethylene triamine, dipropylene triamine, triethylene tetramine, tripropylene tetramine, tetraethylene pentamine, tetrapropylene pentamine, etc.

In the triallylcyanurate aminolysis reaction, the monoprimary or biprimary amines may be used, for example, in proportions from about 1 to 2 moles per mole of triallylcyanurate.

The reaction with 1 mole of amine may conform with the following scheme: ##STR3##

Optionally the reaction may be repeated with at least one part of product (I), according to the following scheme: ##STR4##

Moreover, for biprimary amines, the amine proportion may be, for example, about 0.5 mole per mole of triallylcyanurate and the reaction may comply with the following scheme: ##STR5##

It may still be considered to react the so-obtained product with a monoprimary or biprimary amine ##STR6## in a proportion of 1, 2 or 3 moles per mole of product (III) as above-defined (i.e. about 0.5, 1 or 1.5 moles per mole of initial triallylcyanurate).

The conditions of the triallylcyanurate aminolysis reaction are known. They have been disclosed in particular by H. AHNE and coll. in "Synthesis", March 1975, pages 182-185, the reactant proportions being adjusted according to the desired stoichiometry. Thus, the amino compound (monoprimary and/or biprimary) is used in such a proportion that, as a whole, at least one allyl double bond per molecule remains in each product obtained. Otherwise stated, the products comprising one triazine ring may be mono-or di-substituted and each of the products comprising two triazine rings may have two mono- or di-substituted rings, or even at most one of the two rings may be tri-substituted. In fact, the aminolysis of triallylcyanurate gives products having various substitution degrees which are difficult to separate. They may however be used as such in copolymerization, after removal by distillation of the allyl alcohol formed.

The acrylic ester involved in the formation of the copolymer compositions of the invention, consists more particularly of a linear or branched alkyl portion acrylate or methacrylate containing 1-22 carbon atoms in the alkyl, alkyl methacrylates being preferred.

The acrylic esters may be used alone or as mixtures. Thus, it is advantageous to use at least one relatively light alkyl methacrylate (e.g. whose alkyl group has 1-4 carbon atoms) and at least one relatively heavier alkyl methacrylate (e.g. whose linear alkyl group has 8-22 carbon atoms). More particularly, all the alkyl methacrylates may include about 5-25% by weight of at least one linear or branched C₁ -C₄ alkyl methacrylate, about 10-80% by weight of at least one linear C₈ -C₁₄ alkyl methacrylate and about 15-75% by weight of at least one linear C₁₆ -C₂₂ alkyl methacrylate. The percentages by weight are indicated in proportion to the total amount of methacrylates.

The vinylaromatic monomer optionally involved may consist for example of styrene, α-methyl styrene or vinyltoluene, styrene being preferred.

The copolymer compositions of the invention may be prepared by radical copolymerization from monomers in suitable proportions.

The copolymerization is initiated by a conventional radical initiator such as those currently used in this type of polymerization (azoic or peroxidic compound).

The co-polymerization temperature ranges from 80° to 130° C., the solvent being for example a mineral oil (100 or 200N) used in an amount of 20-50% by weight in proportion to the reaction medium, taken as a whole.

The weight average molecular weight of the products according to the invention may range for example from 30,000 to 800,000 (as determined by chromatography by gel permeation calibrated with methyl polymethacrylate). Their polydispersity is generally lower than 5.

The copolymer compositions according to the invention are used as viscosity additives for lubricating, mineral or synthetic oils. They are generally added in amounts ranging from 0.5 to 10% by weight in proportion to the lubricating oil.

EXAMPLES

The following examples are given to illustrate the invention and must not be considered as limiting the scope thereof.

Examples 19 to 24 are given for comparison purpose. Examples 1 to 8 describe the preparation of nitrogenous monomers derived from triallylcyanurate, used in the preparation of the copolymers according to the invention.

EXAMPLES 1 TO 8 (PREPARATION OF NITROGENOUS MONOMERS)

10 g (40 millimoles) of triallylcyanurate (TAC) are reacted with the amine indicated in Table 1 hereinafter, in the reported molar amount. The reactions are conducted in the absence of solvent at a temperature ranging from 40° to 70° C., for about 30 hours.

For each of the products obtained, the substitution degree of triallylcyanurate has been determined from the amount of allyl alcohol recovered by vacuum distillation at the end of the reaction. As shown in table 1, the selected molar proportions being taken into account, this average substitution degree may be close to 1 (products of example 1 and 3 with 2 triallylcyanurate rings linked by substantially one biprimary amine molecule) or close to 2 (products having one triallylcyanurate ring substituted with about 2 molecules of monoprimary amine --examples 5 to 8-- or with about 2 molecules of biprimary amine --examples 2 and 4).

                  TABLE 1                                                          ______________________________________                                         ex-                                                                            am-  Amino Compound           substitution                                     ple  (H.sub.2 N--A--NR.sup.2).sub.x R.sup.1 (*)                                                          amount  degree                                       No   x     n     m   --A--        mmol  of TAC                                 ______________________________________                                         1    4     0     0   --CH.sub.2 --CH.sub.2 --                                                                    20    1.05                                   2    4     0     0   --CH.sub.2 --CH.sub.2 --                                                                    80    1.95                                   3    3     0     0   --CH.sub.2 --CH.sub.2 --                                                                    20    1.06                                   4    3     0     0   --CH.sub.2 --CH.sub.2 --                                                                    80    1.98                                   5    1     18    0   --CH.sub.2 --CH.sub.2 --CH.sub.2 --                                                         80    1.8                                    6    1     1     1   --CH.sub.2 --CH.sub.2 --CH.sub.2 --                                                         80    1.96                                   7    1     2     2   --CH.sub.2 --CH.sub.2 --CH.sub.2 --                                                         80    1.95                                   8    0     18    0   --           80    1.95                                   ______________________________________                                          (*) It is recalled that, in the amino compound formula, each of R.sup.1        and R.sup.2 may represent the hydrogen atom or an alkyl radical:               respectively C.sub.n H.sub.2n+1 and C.sub.m H.sub.2m+1 (with each of n an      m ranging from 1 to 24). When R.sup.1 or R.sup.2 represents the hydrogen       atom, the reported value of n or m is 0.                                 

EXAMPLES 9 TO 24

Examples 9 to 18 describe the preparation of copolymer compositions according to the invention, using nitrogenous monomers prepared as described in examples 1 to 8, several methacrylates (methyl methacrylate --in short MMA--, lauryl methacrylate-- in short LM--, and styrene methacrylate--, in short SM) and styrene in the proportions by weight indicated in Table 2. In examples 19 to 24, by way of comparison, various copolymers have been prepared without using nitrogenous monomers such as those involved in examples 9-18, or by using other nitrogenous monomers: N-vinylpyrrolidone (in short NVP), N-vinylimidazole (in short NVI), triallylcyanurate (in short TAC) and various combinations of these monomers. The proportions by weight of monomers involved in these comparative examples are also indicated in Table 2.

In these examples, "lauryl methacrylate" and "stearyl methacrylate", as used, are alkyl methacrylate cuts, respectively of 8-18 and 14-22 carbon atoms, whose composition by weight is as follows:

    ______________________________________                                         Lauryl methacrylate (in short LM)                                              13% (±2%)  of C.sub.8 alkyl methacrylate                                    16% (±2%)  of C.sub.10 alkyl methacrylate                                   29% (±2%)  of C.sub.12 alkyl methacrylate                                   21% (±2%)  of C.sub.14 alkyl methacrylate                                   14% (±2%)  of C.sub.16 alkyl methacrylate                                   7% (±2%)   of C.sub.18 alkyl methacrylate                                   Stearyl methacrylate (in short SM)                                             2% (±2%)   of C.sub.14 alkyl methacrylate                                   51% (±2%)  of C.sub.16 alkyl methacrylate                                   30% (±2%)  of C.sub.18 alkyl methacrylate                                   14% (±2%)  of C.sub.20 alkyl methacrylate                                   3% (±2%)   of C.sub.22 alkyl methacrylate                                   ______________________________________                                    

                                      TABLE 2                                      __________________________________________________________________________          nitrogenous     MMA LM  SM  Styrene                                       Example                                                                             monomer         % by                                                                               % by                                                                               % by                                                                               % by                                          No   No       % by weight                                                                           weight                                                                             weight                                                                             weight                                                                             weight                                        __________________________________________________________________________      9   1        1      8   59  32  0                                             10   1        1      6   48  20  25                                            11   1        3.7    7   48.3                                                                               21  20                                            12   2        1      8   49  22  20                                            13   3        3.7    6   46.3                                                                               19  25                                            14   4        3.7    7   48.3                                                                               21  20                                            15   5        3.7    7   48.3                                                                               21  20                                            16   6        1      8   49  22  20                                            17   7        3.5    7   48.5                                                                               21  20                                            18   8        3.5    6   46.5                                                                               19  25                                            19*  --       0      8   50  22  20                                            20*  NVP      3.7    7   48.3                                                                               21  20                                                  2NVP                                                                     21*           3.7    7   48.3                                                                               21  20                                                 1NVI                                                                      22*  TAC      1.7    8   49  21.3                                                                               20                                            23*  TAC      3.7    7   48.3                                                                               21  20                                            24*  TAC +    3.7    7   47.3                                                                               20  20                                                 2NVP/1NVI                                                                               2                                                                __________________________________________________________________________      *comparative examples                                                    

The weight molecular weights of the products range from 200,000 to 400,000 (as determined by chromatography by gel permeation calibrated with methyl polymethacrylate); the polydispersity of products of examples 9-18 ranges from 2.7 to 4.7.

Typical conditions for obtaining copolymers as described in examples 9 to 19, 22 and 23 are the following:

Into a heating reactor provided with mechanical stirring means, a vacuum port and a circulation of inert gas, are introduced:

    ______________________________________                                         Solvent:      100 N oil           25% by weight                                              MMA                                                                            LM                  74.5% by weight                                            SM                  (distribution                                Monomers      Styrene (except ex. 9)                                                                             according                                                  nitrogenous comonomer                                                                              to table 2)                                                (except ex. 19)                                                  Radical initiator (benzoyl peroxide)                                                                   0.5% by weight.                                        ______________________________________                                    

The reactor is thoroughly degased by subjecting it successively to a reduced pressure and to a light pressure of inert gas. The reactor is then heated to 100° C. for 5 hours under stirring; then the temperature is increased up to 130° C. for 2 hours, so as to complete the initiator decomposition and to polymerize monomer residues, if any.

The copolymer compositions of comparative examples 20, 21 and 24 are prepared according to an identical operating mode with introduction of NVI and/or NVP at the end of the polymerization.

EXAMPLE 25 (determination of the additive properties)

Various properties of the additives, prepared in examples 9 to 18 according to the invention and in comparative examples 19 to 24, are defined as follows:

a) Thickening power (in short TP) of the additive. It is defined as the amount of additive to dissolve in a 200N oil for reaching the viscosity of 15 mm² /s at 100° C.

b) Pour point of a 200N oil comprising a proportion of additive determined according to (a) and measured according to standard AFNOR T60 105.

c) Shearing strength of 200N oil comprising the above additive proportion. It is determined by a test in ORBAHN injector according to standard DIN 51382 after 30 cycles; it is expressed by the relative loss of kinematic viscosity (-Δη %).

d) Additive dispersing power. The dispersing efficiency of the compositions according to the invention is evaluated by the dispersion spot test on filter paper, in the presence of carbonaceous material originating from Diesel engine used oil. The ratio between the respective diameters of the black spot and of the oil aureole is determined after 48 hours, the mixture being subjected, before deposition on filter paper, to different treatments.

The quotations retained for this test are the following:

    ______________________________________                                         Sludge-spot diameter                                                           oil-spot diameter                                                                               quotation                                                                               dispersion                                           ______________________________________                                         <32%             0        none                                                 32-39%           1        very low                                             40-56%           2        poor                                                 57-68%           3        mean                                                 68-74%           4        good                                                 ≧75%      5        very good                                            ______________________________________                                    

The results of these determinations are indicated in the following tables 3 and 4.

                  TABLE 3                                                          ______________________________________                                                    TP             Pour                                                 Additive of                                                                               %              point  -Δη                                 example    by weight      (°C.)                                                                          %                                             ______________________________________                                          9         4.2            -33    30                                            10         4.1            -24    17                                            11         3.7            -27    24                                            12         4.3            -30    18                                            13         3.8            -24    20                                            14         4.7            -27    17                                            15         4.5            -27    17                                            16         4.3            -27    18                                            17         4.1            -27    19                                            18         4.8            -24    15                                            19*        3.05           -30    30                                            20*        3.8            -30    20                                            21*        3.3            -27    24                                            22*        3.7            -30    20                                            23*        3.5            -30    23                                            24*        3.05           -30    25                                            ______________________________________                                          *Comparative examples                                                    

                  TABLE 4                                                          ______________________________________                                         Addi- Dispersing efficiency                                                    tive  without H.sub.2 O with H.sub.2 O                                         of ex-        200° C./                                                                         250° C./                                                                       20°                                                                          200° C./                                                                       200° C./                      ample 20° C.                                                                          10'      10'    C.   1'     10'                                  ______________________________________                                          9    4       3        3      4    3      3                                    10    4       3        3      3    4      3                                    11    4       3        3      4    4      4                                    12    4       4        4      4    4      4                                    13    5       5        4      5    5      4                                    14    4       4        4      4    4      4                                    15    4       4        3      4    4      4                                    16    4       4        4      4    4      4                                    17    4       4        4      4    5      4                                    18    4       4        3      4    3      3                                    19*   1       1        1      1    0      1                                    20*   3       2        2      3    3      2                                    21*   3       3        3      3    3      3                                    22*   2       1        1      2    1      1                                    23*   2       1        1      2    1      1                                    24*   3       3        3      3    3      3                                    ______________________________________                                          *Comparative examples                                                    

According to Table 4, it appears that, under the test conditions selected and for the indicated distributions of methacrylic and styrenic recurrent units, the incorporation of nitrogenous monomers with the preparation of the copolymers according to the invention gives good dispersing properties to the resultant additives.

Example 19 shows that the copolymer prepared in the absence of nitrogenous monomer has but a very low dispersing efficiency. Examples 20 and 21 relate to copolymers grafted according to conventional techniques with the usual NVP and NVI monomers.

Examples 22 and 23 show the very low efficiency of triallylcyanurate when incorporated as such with the additive.

Example 24 relates to a copolymer prepared by grafting a mixture of 2/3 NVP and 1/3 NVI on a copolymer such as that of example 23. The previous incorporation of TAC does not improve the dispersing efficiency obtained by introduction of the mixture of NVP and NVI at the end of the polymerization (compare with example 21).

Examples 9 to 18 relate to copolymers according to the invention and illustrate the variety of possible structures of nitrogenous monomer characterizing the invention and of copolymer compositions including it.

EXAMPLE 26

In order to ascertain that the dispersing efficiency depends effectively on the nitrogenous groups fixed on the polymer, the products of examples 11, 15 and 16 have been treated by dialysis for removing the monomers which were not copolymerized or the polymers of low molecular weight.

The dialysis is performed by using, as the solvent, cyclohexane at reflux. After separation, the polymer fraction is precipitated into methanol, dried and again dissolved into 200N oil.

After dialysis, it appears that the polymer of high molecular weight amounts to more than 95% by weight of the monomers initially introduced and that the dispersing efficiency of the polymer after dialysis is identical to that of the initial polymer solution. 

What is claimed as the invention is:
 1. A lubricating composition comprising a major proportion of lubricating oil and a minor proportion, sufficient to improve the viscosity properties thereof, of at least one copolymer composition comprising (a) 55-99.8% by weight of recurrent units derived from at least one acrylic or methacrylic ester and (b) 0.2-10% by weight of recurrent units derived from at least one nitrogenous vinyl monomer obtained by reacting triallylcyanurate with at least one monoprimary or biprimary aliphatic amine, complying with the general formula: ##STR7## wherein R¹ is a hydrogen atom or an alkyl radical --C_(n) H_(2n+1), in which n is an integer from 1 to 24, x ranges from 1 to 10 or may be O when n is at least 4, R² is a hydrogen atom or an alkyl radical --C_(m) H_(2m+1), m being an integer from 1 to 24, and A is an alkylene group of 2-6 carbon atoms, said nitrogenous vinyl monomer containing 1 or 2 triazine rings and comprising at least one allyl group; and (c) 0-35% by weight of a vinyl aromatic monomer.
 2. A lubricating composition according to claim 1, wherein said vinylaromatic monomer is styrene.
 3. A lubricating composition according to claim 1, wherein said acrylic or methacrylic ester consists of at least one linear or branched alkyl acrylate or methacrylate having 1 to 22 carbon atoms in the alkyl group.
 4. A lubricating composition according to claim 1, wherein the copolymer composition has a weight average molecular weight from about 30,000 to 800,000 and a polydispersity lower than
 5. 5. A lubricating composition according to claim 1, wherein said nitrogenous vinyl monomer results from the reaction of about 1 to 2 moles of monoprimary or biprimary amine per mole of trialkylcyanurate, with removal of the allyl alcohol formed.
 6. A lubricating composition according to claim 1, wherein said nitrogenous vinyl monomer results from the reaction of about 0.5 mole of biprimary amine per mole of triallylcyanurate, with removal of the allyl alcohol formed.
 7. A lubricating composition according to claim 6, wherein the amount of copolymer composition is from 0.5 to 10% by weight in proportion to the lubricating oil.
 8. A lubricating composition according to claim 2, wherein said acrylic or methacrylic ester consists of at least one linear or branched alkyl acrylate or methacrylate having 1 to 22 carbon atoms in the alkyl group.
 9. A lubricating composition according to claim 8, wherein the copolymer has a weight average molecular weight from about 30,000 to 800,000 and a polydispersity lower than
 5. 10. A lubricating composition according to claim 9, wherein the nitrogenous vinyl monomer is obtained by reacting 1-2 moles of the monoprimary or biprimary amine with one mole of triallylcyanurate.
 11. A lubricating composition according to claim 9, wherein said nitrogenous vinyl monomer is obtained by reacting triallylcyanurate with at least one monoprimary aliphatic amine.
 12. A lubricating composition according to claim 9, wherein said nitrogenous vinyl monomer is obtained by reacting triallylcyanurate with at least one biprimary aliphatic amine.
 13. A lubricating composition according to claim 11, wherein said monoprimary aliphatic amine is n-butylamine, secbutylamine, tert-butylamine, n-pentylamine, 4, 3 or 2 methyl-n-butylamine, n-hexylamine, n-heptylamine, n-octylamine, n-nonylamine, eicosylamine, docosylamine, N,N-dimethyl diaminoproprane, or N,N-diethyl diamino-isopropane.
 14. A lubricating composition according to claim 12, wherein the biprimary aliphatic amine is ethylene diamine, propylene diamine, diethylene triamine, dipropylene triamine, triethylene tetramine, tripropylene tetramine, tetraethylene pentamine, or tetrapropylene pentamine.
 15. A lubricating composition comprising a major proportion of lubricating oil and a minor proportion, sufficient to improve the viscosity properties thereof, of at least one copolymer composition comprising:(a) 55 to 99.8% by weight of at least one linear or branched alkyl acrylate or methylacrylate having 1-22 carbon atoms in the alkyl group; (b) 0.2-10% by weight of ##STR8## wherein R¹ is a hydrogen atom or an alkyl radical --C_(n) H_(2n+1), in which n is an integer from 1 to 24, x ranges from 1 to 10 or may be a 0 when n is at least 4, R² is a hydrogen atom or an alkyl radical --C_(m) H_(2m+1), m being an integer from 1 to 24, and A is an alkylene group of 2-6 carbon atoms, and R³ represents CH₂ ═CH--CH₂ --; and (c) 0-35% by weight of a vinyl aromatic monomer.
 16. A lubricating composition according to claim 15, wherein said monomer (b) is present in the copolymer in an amount of 0.5-4% by weight and said vinyl aromatic monomer is styrene in an amount of above 0% by weight. 